8158

• UCREFRP Catalog Number: 8158
• Author: Osmundson, D. B.
• Title: Longitudinal Variation in Fish Community Structure and Water Temperature in the Upper Colorado River; Final Report.
• USFW Year: 1999.
• USFW - Doc Type: Grand Junction, Colorado.
• Copyright Material: NO

Table 1. Length-weight regression coefficients used in calculation of relative condition of
three native species (bluehead sucker, flannelmouth sucker and roundtail chub). Fish were
captured from the Colorado and Gunnison rivers during Eg,'W, ing and fall of 1994 and 1995.
Relative condition (Kn) was expressed as Kn = 100 x M e where M. is the observed mass
(g) and K is the expected mass (g) as calculated from: = Log,a(length)- m + b.
Length is measured in mm.
Species N Slope(m) (SE) y-intercept(b) (SE) k
Bluehead
sucker 4430
Flannelmouth
sucker 3949
Roundtail
chub 562
3.07693 (0.007) -5.19342 (0.017) 0.978
3.08837 (0.005) -5.24830 (0.014) 0.988
3.09617 (0.017) -5.30952 (0.041) 0.984
Longitudinal variation in condition for each species varied somewhat by sampling period (see
Appendix Figures 1-3). For bluehead sucker, condition increased in an upstream direction
fairly consistently among periods (Appendix; Figure 1; Appendix Table 11) . This was
generally the case for flannelmouth suckers during fall of each year, but not during spring
when condition was similar throughout the Colorado River (Appendix Figure 2; Appendix
Table 12). Condition of bluehead and flannelmouth suckers was significantly higher in the
Gunnison River stratum than in any Colorado River stratum group in fall 1994 and spring
1995. However, condition of both sucker species in fall 1995 was similar between the
Gunnison River stratum and the upper five Colorado River strata. For roundtail chubs, small
sample size and sizable variation among individuals resulted in no consistent longitudinal
patterns among seasons (Appendix Figure 3; Appendix Table 13).
Temporal Variation
Although data were somewhat limited (two seasons in each of two years), there was a pattern
of higher condition during early spring and lower condition during fall (Figure 12; Appendix
Table 14). For flannelmouth sucker and roundtail chub, condition significantly declined by fall
of each year. For bluehead sucker, this same pattern was exhibited in 1994, but not in 1995:
relative condition was similar in spring and fall of 1995.
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